1. Field of the Invention
This invention relates to a chair of the type which has a rearwardly tiltable seat back.
2. Description of the Related Art
There are various types of chairs which include arm chairs, rocking chairs, and etc. In designing any type of chair, primary attention is given to ensure that the seat occupant is comfortably seated for a long time, taking the human technology into consideration.
U.S. Pat. No. 4,685,733 to Machate et al discloses a rocking chair wherein the seat back has a waist supporting portion which bulges progressively forward as the seat back tilts rearward. If the waist supporting portion of the seat back bulges to a reasonable extent (which is the case when the seat back tilts only halfway), it provides a comfortable support for the seat occupant. However, if the waist supporting portion bulges excessively, the seat occupant feels uncomfortable or uneasy because his or her torso is rearwardly bent sharply at the back. Such a problem often occurs when the seat back tilts fully rearward.
Japanese Patent Application laid-open No. 2-46811 (Laid-open: Feb. 6, 1990) discloses a similar rocking chair.
Japanese Patent Application laid-open No. 2-45012 (laid-open: Feb. 15, 1992) discloses a rocking chair wherein the seat back has a waist supporting portion which bulges progressively forward upon tilting of the seat back, and wherein the seat is made to translationally move forward as the seat back tilts forward. In addition to the disadvantage discussed above, this chair has been found to have another disadvantage that the clothing (e.g. shirt) of the seat occupant is pulled as the seat moves translationally forward.
Japanese Patent Application laid-open No. 4-58905 (Laid-open: Feb. 25, 1992) also discloses a rocking chair which is similar to that disclosed in Japanese Patent Application laid-open No. 4-45012 discussed above.